How to write mod_rewrite rules for apache

Hi I'm using Zend Framework with the following .htaccess file to route all traffic through my index.php page (except for images, css etc).
I need to also make a particular directory exempt from the mod_rewrite, or alternatively files ending in .doc, .pdf .rtf.

The existing .htaccess file looks like this:

RewriteEngine On

RewriteCond %{REQUEST_FILENAME} -s [OR]

RewriteCond %{REQUEST_FILENAME} -l [OR]

RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^.*$ - [NC,L]

RewriteRule ^.*$ index.php [NC,L]

Code (markup):

Even if someone can recommend a good tutorial for learning how to write mod_rewrite rules that would be really useful.

Thanks in advance.

Tony

 

Any of these top listings are a good start.